The present invention relates to a camera having an automatic exposure control means and, more particularly, to a method of supplying exposure control information into an automatic exposure control means.
Various types of means for electrically controlling the operation of electronic devices on the basis of various kinds of information supplied thereinto in the form of electric signals have been proposed in recent years.
When the input signal is an analog one, it is usually converted into a digital one by using an analog to digital converter (which will be hereinafter referred to as A-D converter) so as to stabilize the input signal and effect the transmission thereof at a high accuracy.
It has been proposed to apply this method to cameras. In such an application, the method has the steps of: introducing thereinto various kinds of exposure control information, such as an aperture value, shutter speed, ASA sensitivity (sensitivity of film), and opened aperture value as analog signals based on changes in voltage; converting the signals into digital ones in the manner as mentioned above; and processing the digital signals in a control circuit including an exposure control arithmetic means. Since the capacity of the power source of the camera is limited, the feeding of the electric power to an automatic exposure control means and to circuits for processing signals or receiving and computing exposure control information is conducted when the shutter release for causing a shutter action for photographing is operated, in order to avoid the consumption of electric power of the power source while the camera is not in use.
It is therefore necessary that the processing of signals such as inputting and computing of the above-mentioned information is conducted in quite a short period of time which starts with the start of operation of the shutter release and ends with the start of operation of the shutter.
In a conventional camera, the conversions of signals are carried out by different A-D converters for different types of exposure control information, to assure the accuracy of the information. However, in such a method, a corresponding number of A-D corresponding converters to the number of types of exposure control informations are required. This causes the exposure control circuit to be complicated and brings about an increase in manufacturing cost.
A method has been proposed in which the set values of the photographing information are input in the form of codes, but this method is disadvantageous in that it requires an increased number of pins in an integrated circuit (IC) of the automatic control means, which also causes an increase in manufacturing cost.